The invention relates to improvements in winders for winding a roll from a continuous traveling web, and more particularly to improvements in paper web winders such as used on paper making machines or used in paper web converting operations.
In high speed winding wherein a roll is wound from a web of paper onto a core, the web will travel at speeds of 4,000 to 6,000 feet per minute, and it is imperative that the winding progress uniformly so as to maintain a constant tension of the web on the roll and insure that the roll is uniform. With changes in size of the roll as its size increases, the effects of the supporting and driving mechanism change so that control becomes difficult. One of the phenomena which occurs is vibration or bouncing of the roll, and this is a term used to describe two common modes of vibration. These modes are radial which is a repetitive radial motion, sometimes called buzzing, against a winding drum which affects wound roll speed and quality. Another adverse effect is rocking, which is an arc-like repetitive angular motion, sometimes known as thumping, which occurs with respect to the winding drum, and this is a less frequent problem than the radial motion. The bouncing or vibration of the paper roll in a double drum winder wherein the roll is supported on two parallel drums is a cause for reduced production during the winding operation. The paper maker observes the problem as audible buzzing or a rocking thumping back and forth on the winding drums. He will attempt to adjust tension on the web or pressure of the rider roll on top of the wound roll to control the bouncing generally with little success. It then becomes necessary to reduce speed until the buzzing or thumping is controlled. This vibration or bouncing not only causes production difficulties requiring slowing of winding, but it also creates maintenance problems. As to the mechanism itself, looseness of parts will occur, foundation cracks and excessive wear and fatigue of the metal of parts can occur. This operation with accompanying bouncing can also be extremely dangerous to personnel in the vicinity of the winder because of the high kinetic energy of a roll rotating from 4,000 to 6,000 feet per minute when the roll weighs several thousand pounds. The disturbance in the roll continues to be generated around the circumference of the roll until it closes to form a repeating cycle. Thus, the bouncing becomes a harmonic of the wound roll rotation. The initial disturbance may be caused by many factors including uneven paper surface, machine direction basis weight variations, caliper variations, eccentric starts, variations in paper or paper to steel frictional characteristics, glue, unwinder drums and winder chevrons. Once this disturbance occurs, the next disturbances which follow are related to the energy available or the deformable nature, diameter and roll characteristics (friction) of the wound roll.
Adjusting tension or rider roll pressure is in effect an attempt at changing the deformable nature of the paper roll. It is difficult to have much control over the problem by making these adjustments. A poorly wound roll is generally the only result.
Reducing the rewinding roll speed generally reduces the tendency for the initial disturbance to deform the roll, and it reduces energy available to sustain the vibration. It is a means of stopping winder bounce, but does not result in being able to maintain production speeds.
The two drum winder actually presents a mass elastic system which can be envisioned as consisting of a rotatable mass having deformable springs on fixed drums. That is, the reaction force between the supporting drums and the roll is resilient in nature having a spring constant. With this, the natural frequencies can be calculated. These natural frequencies change with change in roll size. The rider roll engaging the top of the wound roll provides another force relationship which interacts with a spring constant. Thus, the resiliency of the roll engaged at three points of support, i.e., the two supporting drums, and the rider roll, provides an unstable unit.
Efforts to control bouncing have included adding a vibration absorber to the rider roll, but this has not proven to fully solve the problem.
It is accordingly an object of the present invention to provide an improved paper web winder which is capable of high speed continuous winding operation without bouncing and without the deleterious winding effects caused by such bouncing.
A further object of the invention is to provide an improved two drum winder which is capable of compensating for a change in springiness factor of the wound roll during winding.
Other objects, advantages and features, as well as equivalent structures and methods which are intended to be covered herein, will become more apparent with the teaching of the principles of the invention in connection with the disclosure of the preferred embodiments in the specification, claims and drawings, in which: